Ion channels and transporters are membrane proteins selectively permeable to ions, small olecular nutrients and metabolites. These proteins are critical to a variety of biological processes and represent a large class of therapeutic targets. Bioactive small molecules are a key source for identification of life-altering Pharmaceuticals and life science discovery probes. Different from many protein classes, ion channels and transporters often require special instruments and unique experimental expertise in order to perform analyses. Thus, carrying out large-scale compound library screens for ion channels has posed a considerable challenge. Johns Hopkins ChemCORE is a fully operational, high throughput compound screening facility with a strong combination of scientific excellence, operational productivity, and ion channel expertise. Hence, the existing operation at Hopkins is ideally suited to contribute the production phase of the Molecular Libraries Probe Production Centers Network (MLPCN). We therefore propose to form the Johns Hopkins Ion Channel Center (JHICC) - "Specialized Screening Center" JHICC will meet the following specific aims: (1) to screen large diverse molecular libraries of 300,000 or more compounds against each of thefive important ion channel/transporter targets assigned by NIH, (2) to actively collaborate with chemists in other network centers to maximize probe development and production, (3) to disseminate the resulting information to the public domain (PubChem), and (4) to perform Center-driven research projects with significant impact on molecular probe discovery and development. By maximizing its quality and productivity and by adhering to MLPCN governance mechanisms, JHICC will be a responsible and highly productive member of the MLPCN and NIH Roadmap Initiative.